This invention relates to an ultraviolet radiation curable liquid composition particularly adapted for the formation of protective coating on heat degradable electronic components. In particular, this invention relates to an ultraviolet hardenable resin composition particularly adapted for providing a protective coating on heat sensitive axial leaded or radial leaded film/foil or metallized capacitors and to the resultant coated capacitors.
In order to protect electronic components from various harmful aspects of the environment such as dirt, moisture, extremes in temperature, shock, abrasion and printed circuit cleaning solvents, it has long been the practice to protect these components with various hardened coating compositions. When the ingredients of the electronic component are such that they are not degradable at low temperatures, it has subsequently been found satisfactory to apply a heat hardenable resin composition. In many cases, however, the composition of the electronic component are such that they are degradable at relatively low temperatures frequently below the temperatures employed in hardening the heat hardenable resin compositions and wave soldering. In such cases, ultraviolet radiation curable compositions have frequently been employed. While ultraviolet radiation curable compositions have been found to be useful for many electronic components, it has been found that the heat of reaction is in some cases in excess of the degradation temperature of the component. This has been found particularly true when the component contains such materials as polystyrene or polypropylene. Thus, there is a need for a rapid curing low temperature U.V. curable coating composition for axial or radial leaded film/foil or metallized capacitors containing polypropylene or polystyrene film.